Pfizerpen Dosage

Generic name: PENICILLIN G POTASSIUM 5000000[iU]
Dosage form: injection, powder, for solution
Drug class: Natural penicillins

Medically reviewed by Drugs.com. Last updated on Aug 27, 2024.

Buffered Penicillin G Potassium for Injection, USP may be given intravenously or intramuscularly. The usual dose recommendations are as follows:

Adult patients

CLINICAL INDICATION	DOSAGE
* Because of its short half-life, Penicillin G is administered in divided doses, usually every 4–6 hours with the exception of meningococcal meningitis/septicemia, i.e., every 2 hours.
Serious infections due to susceptible strains of streptococci (including S. pneumoniae) -septicemia, empyema, pneumonia, pericarditis, endocarditis and meningitis	12 to 24 million units/day depending on the infection and its severity administered in equally divided doses every 4–6 hours.
Serious infections due to susceptible strains of staphylococci -septicemia, empyema, pneumonia, pericarditis, endocarditis and meningitis	5 to 24 million units/day depending on the infection and its severity administered in equally divided doses every 4–6 hours.
Anthrax	Minimum of 8 million units/day in divided doses every 6 hours. Higher doses may be required depending on susceptibility of organism.
Actinomycosis
Cervicofacial disease	1 to 6 million units/day*
Thoracic and abdominal disease	10 to 20 million units/day*
Clostridial infections
Botulism (adjunctive therapy to antitoxin) Gas gangrene (debridement and/or surgery as indicated) Tetanus (adjunctive therapy to human tetanus immune globulin)	20 million units/day*
Diphtheria (adjunctive therapy to antitoxin and for the prevention of the carrier state)	2 to 3 million units/day in divided doses for 10–12 days*
Erysipelothrix endocarditis	12 to 20 million units/day for 4–6 weeks*
Fusospirochetosis (severe infections of the oropharynx [Vincent's], lower respiratory tract and genital area)	5 to 10 million units/day*
Listeria infections
Meningitis	15 to 20 million units/day for 2 weeks*
Endocarditis	15 to 20 million units/day for 4 weeks*
Pasteurella infections including bacteremia and meningitis	4 to 6 million units/day for 2 weeks*
Haverhill fever; Rat-bite fever	12 to 20 million units/day for 3–4 weeks*
Disseminated gonococcal infections, such as meningitis, endocarditis, arthritis, etc., caused by penicillin – susceptible organisms	10 million units/day*; duration depends on the type of infection
Syphilis (neurosyphilis)	12 to 24 million units/day, as 2–4 MU every 4 hours for 10–14 days; many experts recommend additional therapy with Benzathine PCN G 2.4 MU IM weekly for 3 doses after completion of IV therapy
Meningococcal meningitis and/or septicemia	24 million units/day as 2 million units every 2 hours

Pediatric patients

This product should not be administered to patients requiring less than one million units per dose (see Precautions-Pediatric Use).

CLINICAL INDICATION	DOSAGE
Serious infections, such as pneumonia and endocarditis, due to susceptible strains of streptococci (including S. pneumoniae) and meningococcus	150,000–300,000 units/kg/day divided in equal doses every 4–6 hours; duration depends on infecting organism and type of infection
Meningitis caused by susceptible strains of pneumococcus and meningococcus	250,000 units/kg/day divided in equal doses every 4 hours for 7–14 days depending on the infecting organism (maximum dose of 12–20 million units/day)
Disseminated Gonococcal Infections (penicillin-susceptible strains)	Weight less than 45 kg:
Arthritis	100,000 units/kg/day in 4 equally divided doses for 7–10 days
Meningitis	250,000 units/kg/day in equal doses every 4 hours for 10–14 days
Endocarditis	250,000 units/kg/day in equal doses every 4 hours for 4 weeks
Arthritis, meningitis, endocarditis	Weight 45 kg or greater: 10 million units/day in equally divided doses with the duration of therapy depending on the type of infection
Syphilis (congenital and neurosyphilis) after the newborn period	200,000–300,000 units/kg/day (administered as 50,000 units/kg every 4–6 hours) for 10–14 days
Diphtheria (adjunctive therapy to antitoxin and for prevention of the carrier state)	150,000–250,000 units/kg/day in equal doses every 6 hours for 7–10 days
Rat-bite fever; Haverhill fever (with endocarditis caused by S. moniliformis)	150,000–250,000 units/kg/day in equal doses every 4 hours for 4 weeks

Renal Impairment

Penicillin G is relatively nontoxic, and dosage adjustments are generally required only in cases of severe renal impairment. The recommended dosage regimens are as follows:

Creatinine clearance less than 10 mL/min/1.73m2; administer a full loading dose (see recommended dosages in the tables above) followed by one-half of the loading dose every 8–10 hours.

Uremic patients with a creatinine clearance greater than 10 mL/min/1.73m2; administer a full loading dose (see recommended dosages in the tables above) followed by one-half of the loading dose every 4–5 hours. Additional dosage modification should be made in patients with hepatic disease and renal impairment.

For most acute infections, treatment should be continued for at least 48 to 72 hours after the patient becomes asymptomatic. Antibiotic therapy for Group A β-hemolytic streptococcal infections should be maintained for at least 10 days to reduce the risk of rheumatic fever.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration whenever solution and container permit.

Reconstitution

The following table shows the amount of solvent required for solution of various concentrations:

Approx. Desired Concentration (units/mL)	Volume (mL) Solvent for Vial of 5,000,000 units	Infusion Only Volume (mL) Solvent for Vial of 20,000,000 units
50,000	–	–
100,000	–	–
250,000	18.2	75.0
500,000	8.2	33.0
1,000,000	3.2	11.5

When the required volume of solvent is greater than the capacity of the vial, the penicillin can be dissolved by first injecting only a portion of the solvent into the vial, then withdrawing the resultant solution and combining it with the remainder of the solvent in a larger sterile container.

Buffered Pfizerpen (Penicillin G Potassium for Injection, USP) is highly water soluble. It may be dissolved in small amounts of Water for Injection, or Sterile Isotonic Sodium Chloride Solution for Parenteral Use. All solutions should be stored in a refrigerator. When refrigerated, penicillin solutions may be stored for seven days without significant loss of potency.

Buffered Pfizerpen for Injection may be given intramuscularly or by continuous intravenous infusion for dosages of 500,000, 1,000,000, or 5,000,000 units. It is also suitable for intrapleural, intraarticular, and other local instillations.

THE 20,000,000 UNIT DOSAGE MAY BE ADMINISTERED BY INTRAVENOUS INFUSION ONLY.

(1) Intramuscular Injection

Keep total volume of injection small. The intramuscular route is the preferred route of administration. Solutions containing up to 100,000 units of penicillin per mL of diluent may be used with a minimum of discomfort. Greater concentration of penicillin G per mL is physically possible and may be employed where therapy demands. When large dosages are required, it may be advisable to administer aqueous solutions of penicillin by means of continuous intravenous infusion.

(2) Continuous Intravenous Infusion

Determine the volume of fluid and rate of its administration required by the patient in a 24 hour period in the usual manner for fluid therapy, and add the appropriate daily dosage of penicillin to this fluid. For example, if an adult patient requires 2 liters of fluid in 24 hours and a daily dosage of 10 million units of penicillin, add 5 million units to 1 liter and adjust the rate of flow so the liter will be infused in 12 hours.

(3) Intrapleural or Other Local Infusion

If fluid is aspirated, give infusion in a volume equal to ¼ or ½ the amount of fluid aspirated, otherwise, prepare as for intramuscular injection.

(4) Intrathecal Use

The intrathecal use of penicillin in meningitis must be highly individualized. It should be employed only with full consideration of the possible irritating effects of penicillin when used by this route. The preferred route of therapy in bacterial meningitides is intravenous, supplemented by intramuscular injection.

Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit.

Sterile solution may be left in refrigerator for one week without significant loss of potency.